We are running a Exchange 2010 , which needs to be updated to 2013. In the upgrade process there are some settings which needs to be on AD and so many other objects.
My Question is How can I make sure I won't break existing Server until I'm 100% sure 2013 one is fully operational?
Do I have to run another 2010 Server to be able to provide 2010 and 2013 coexistence?